Decorous supporter losing heart (6)

I believe the answer is:

proper

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'decorous' is the definition.
(associated in meaning)

'supporter losing heart' is the wordplay.
'supporter' becomes 'pro' (I've seen this in another clue).
'losing heart' becomes 'per' (I can't explain this - if you can you should believe this answer much more).
'pro'+'per'='PROPER'

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(Other definitions for proper that I've seen before include "Befitting" , "Suitable or appropriate" , "Correct; formal" , "Appropriate according to rules" , "Right, correct or appropriate" .)

I've seen this clue in The Times.

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